Myford QC Gearbox Project.

[Pete W.]

Hi there, all,

I threatened that I'd get to do some work INSIDE my workshop and here I am at last.          

About five years ago, I bought a Quick Change Gearbox for my ML7 lathe.  Various red herrings and distractions delayed its fitting but it's finally reached the top of the list!

Unfortunately, it turns out that the gearbox that I bought (no fault of the seller) is the Myford Super 7 version, not the ML7 one.  The differences are that the Super 7 Gear Cover won't easily fit the ML7 and the Super 7 lead-screw is 3.4" diameter compared to the 5/8" diameter ML7 version.

Part of the fitting procedure is to shorten the original ML7 lead-screw and I could do that.  But, somewhere along the way, I bought a gear-box-ready 5/8" lead-screw.  I'll get back to lead-screws later, I've decided to start with the Gear Cover.

I was advised that the new proprietors of Myford Ltd. were offering ML7 Gear Covers so I bought one.  The snag is that they are raw castings, un-fettled, no holes drilled and/or tapped and un-painted.  So the first stage is to have a fettle!

(Before anyone clicks on the PM button, I have accepted an offer for the Super 7 Gear Cover.)

The raw casting looks like this:



and



and



and (on this one, if you look carefully, you might spot little pimples on some of the letters - I guess these are the imprints of the heads of the pins that fixed the letters to the pattern)



and



So I have to transform that to something more like this:



and



and



and



The raw casting doesn't have a dotted line labelled 'File to here', that's why I've taken the photos of the Super 7 Cover.  It fitted the back-plate OK so the photos give me a guide as to how much to take off the raw casting.

Watch this space!   

[awemawson]

Glad to see that you are back in the workshop doing engineering rather than roof repairs Pete. It must be a great relief 

Andrew

[Pete W.]

Hi there, all,

I've managed a bit of progress with this project.

I decided that my avatar (the can of peas) was too stationary and was holding me back so I've changed it to something a little more dynamic.  It's from a cigarette card and depicts an Alvis TA14 drop-head coupé which happens to be the car in which I learned to drive.  It had the Tickfords body. 
Wikipedia reckons its maximum speed is in the low 70s but I once had steam coming out of the windscreen demister slots while doing 85 round the Stamford by-pass!          
Needless to say, that was before the 70 mph speed limit was brought in (but not why!!           ) 

Anyway, back to the project:

Here's a view of the ML7 gear cover after fettling:



And here's an extract from the illustrated parts list (aka 'exploded diagram') showing how this part of the machine goes together:



In addition to buying the gear cover raw casting, I've also managed to acquire some of the minor associated parts from various sources. 
Having fettled, I blued the regions that need holes drilling and tapping.  I started on the easy one, the 1/4" Whit tapped hole for the knob.



and



That's all fairly straightforward stuff.  The casting material drillls and taps quite easily so far, not too soft and smeary!  The knob doesn't seat down fully despite my drilling and tapping the hole to a generous depth, I assume there's a swelling where the stud enters the bakelite.  I shall add a fibre washer on final assembly to fill the gap.

Another hole needed is to take the 2 BA by 5/16" screw that secures the clip or latch (part nos 225 & 229 on the exploded diagram).  Here's the relevant location:



I don't have the spring clip to hand so I can't drill that one yet.

The really challenging part of this process is the location of the two 5/16" BSF tapped holes that take the hinge screws (part number 223 on the exploded diagram).  The pointed ends of the screws locate in vee-shaped dimples in the back-plate and I have to transfer the position of those dimples to the two lugs on the gear cover, this photo shows the scene:



Another view:



And another:



The method I have in mind for this operation is to mount the back-plate on a rectangle of MDF so that the points of the dimples (what's the inverse of 'apex'?) align with a line drawn, say, 1.5 inches from the edge of the MDF.  Then, with that MDF resting on a flat surface, to set the scriber point of a scribing block level with the dimple centres.  Then, I shall place the gear cover in position on the back-plate and secure the two parts together (probably with Gaffer tape).  Then, using the scribing block, I shall scribe a horizontal line on each of the outer faces of the gear cover lugs.  The next stage is to reset the scribing block to 1.5 inches and to move the MDF into an upright position, supported by a large angle plate, and scribe again on the outer surfaces of the lugs.  Where these lines intersect on each lug is the position for drilling the holes for the hinge screws.  I hope that the lugs are square enough for the holes to drill true with the lower lug resting flat on the drilling machine table (with a bit of MDF beneath it).

When I get to do all this, I'll take some more photos.  I should quote here the military maxim 'No plan ever survives contact with the enemy!'.

When I've done all this drilling and tapping, it'll be time to paint the gear cover.  I've got some Hammerite special primer, water-based, brush applied, and I also have a rather old can of Myford grey enamel.  I'd welcome any tips and advice on the painting part of the project.

Once the painting is complete, the next job is to fit the change-wheel label which goes here:



rather like this:



The label is supposed to be attached using four very small hammer drive screws.  I haven't got the hammer drive screws yet.  You can see dimples in the casting marking the notional positions of the holes, I hope they're accurate.  I anticipate that care will be required to avoid drilling right through!!

[awemawson]

Looking good Pete, glad to see the new workshop roof is keeping you covered 

"I anticipate that care will be required to avoid drilling right through!!" 

Drill through a length of dowel, slip over your drill and ensure only what you need sticks through.

[Pete W.]

Hi there, all,

I've now marked-out the gear cover lugs for the hinge screws.

Step 1 was to mount the gear cover back-plate on a couple of pieces of MDF.  In the event, I drew my reference line further from the edge of the MDF than I quoted in yesterday's post.   To get the base-plate mounted rock-free I had to accept more overhang than I would have liked but it seemed to go OK - the test will be when I drill and tap the hinge-screw holes!  (There doesn't seem to be a smilie with fingers crossed!!!)  Here's photo #1:



It took a while to get the base-plate correctly positioned with respect to the reference line but eventually I was satisfied it was as close as |I was going to get:



and



The next step was to set the scriber point of the scribing block to the centre of the dimple(s) in the back-plate, like this:



Having done that, I attached the gear cover to the back-plate, using Gaffer tape.  I inserted a few strips of thin cardboard between the back-plate and the gear cover.  Then I scribed a horizontal line on each outer face of the gear cover lugs, like this:



The next step was to up-end the MDF with the back-plate and gear cover and to support them with a large tool-maker's clamp and a heavy angle-plate.  Then I reset the scribing block to the reference line on the MDF, like this:



Then I scribed lines on each outer face of the gear cover lugs, at right angles to the previous lines, like this:



and



I've run out of time for today.  Hopefully, tomorrow afternoon will bring this stage of the project to a conclusion.  Watch this space!! 

[awemawson]

Looking good Pete 

Eccentric bushes will sort you out if it all goes horribly wrong 

[ieezitin]

Pete...

This is coming along nicely........ good work in documenting the marking out and what you had to do, nice use of your marking out kit.

Anthony.

[Pete W.]

Hi there, Andrew and Anthony,
Thank you both for your encouragement.          

Andrew, I have a confession to make:
I didn't do the marking out in the workshop - there isn't YET enough clear bench-space so I did the marking out on the dining table!          

(Fortunately, the table-top is rugged enough to take that sort of abuse, it's real (pre-restrictions) teak, a one time factory planked bench-top that the factory owner had pensioned-off and used for concrete shuttering and then passed on to me.           )

[RadRod67]

Great work, just wondering why Myford don't supply a drawing with a raw casting?

[awemawson]

Myford aren't Myford anymore 

They went to the wall and the name and quite a bit of stock were bought by RDG who promptly tried to stop any one else  using the name Myford on ebay even if it WAS genuine Myford kit.

Made themselves a bit unpopular 

[Pete W.]

Hi there, RadRod67,

Well, this is my understanding of the situation.  I may well have some details wrong but here goes:

The original Myford (I refer to them as 'Beeston Myford' but some others refer to them as 'Nottingham Myford') closed down and the rights to the name and some of the residual stock were bought by RDG who moved the business to a place called Mytholmroyd, not far from Halifax, Yorkshire (West Riding).  You can find their web-site via Google and they also list on eBay.

According to the new proprietors' literature, they aren't currently manufacturing complete lathes but they are (or were) selling complete machines that were included in the stock they bought at the same time as they bought the rights to the Myford name and trademarks.  Most of their current business seems to be the sale of spares.  I bought the black Bakelite knob and the two hinge screws from them as spares.

They recently listed these ML7 Gear Cover castings which I assume were a batch of residual items that came among all the other stuff they received from the Beeston Myford's liquidation sale.  So the castings weren't sold as any sort of kit - it was more a case of 'here they are, raw castings, un-painted and no holes drilled or tapped and no fittings or furniture, sold as described'.  In other words, they were accurately described, warts and all, so I knew what was on offer.  I reckoned I could perform the required operations to get a working gear cover so I bought one.  I might well have spent less money and time if I had bought a 'ready-to-go' gear cover on eBay but I preferred to do it this way.

I don't know how Beeston Myford originally manufactured the Gear Cover and Back-plate, it's difficult to see which feature of the gear cover you could use as a reference to locate the hinge screw holes.  Maybe they jig-drilled the hinge screw holes in the cover, paired the cover to a back-plate and then spotted through to drill the 'dimples' in the back-plate.

I wrote in my earlier post that I would be grateful for any advice or tips regarding the painting of the casting.  I've spent some time this afternoon looking at some of Dan Gelbart's videos on Youtube and I found his video on surface preparation very interesting. 

[Pete W.]

Hi there, all,

Despite sundry distractions, a bit more progress to report:

This post deals with the drilling of the holes for the gear cover hinge-screws - I showed them being marked-out in my last batch of photos.  Since then, with the help of my lovely but shy assistant, I've centre-punched the hole positions and drilled an initial dimple in each lug with a centre drill in a hand-drill.  (I needed my lovely but shy assistant's help because the gear cover is such an awkward shaped thing.)  I want the holes to be fairly precisely in line with each other so I didn't trust myself to drill them by hand, I decided to use the lathe.

The first step was to check the alignment of the tail-stock with respect to the head-stock, like this:



I'm embarrassed about the rust on the 'mandrel protector' (a small chuck back-plate), it's a legacy from the leaky roof.  The steel wool has gone missing and I was eager to get on with the main part of the job!

I bought myself a new angle plate and bolted it to the cross-slide like this (nuts only finger tight at this stage):



And then I drilled and counter-bored a thick slab of MDF and bolted it to the angle plate, like so:



The next stage was to trap the gear cover between head-stock and tail-stock centres and clamp it to the slab of MDF.  This took a bit of fiddling and shuffling but eventually I was satisfied with the positioning and tightened up the G-clamp and the tee-slot bolts securing the angle plate to the cross-slide.  Like this:



Here are a couple of shots of the centres in the gear cover lug dimples:



and



At that stage I ran out of time.  I've ordered some long series centre drills so that having drilled a pilot hole through the lug nearest the head-stock, I can spot-drill the back of the other lug to start the drill for its hole.  In order to avoid any twisting forces on the gear cover and its clamp, I plan to use the tail-stock to push the gear cover + saddle onto the drills held in a drill-chuck in the lathe mandrel.  I'll change to a female centre when the drill approaches breakthrough.

Then all I've got to do is find the 5/16" BSF taps which seem to have been tap-napped by the shed gremlins!          

[Pete W.]

Hi there, all,

Just a quick up-date today, no photos.

I started in at the drilling with a standard BS3 centre drill.  As I wrote in yesterday's post, I used the tail-stock to push the gear cover and saddle.  That worked OK but when I wanted to clear the chips, I wound back the saddle handwheel without first retracting the tail-stock. 
Bad move, the casting moved under the G-clamp!        
It tilted slightly upwards away from the head-stock so when I resumed drilling the centre drill was cutting from the lower flank of the hole.           Fortunately I hadn't drilled very deep at this stage. 

By the time I'd recognised my error, I'd lost the initial dimple in the left-hand lug so I couldn't line up again from scratch - all I could do was slacken the clamp and re-align by eye against the scriber marks.  (There doesn't seem to be a smiley with fingers crossed!)

Anyway, I substituted a 1/4" end mill for the centre drill to flatten the bottom of the hole and give the centre drill a new start into the re-aligned casting.  I then put a 6.5 mm stub drill through that lug and followed that with a long series BS3 centre drill into the inner face of the right-hand lug.  I substituted a female centre for the male tail-stock centre just before the centre drill emerged. 

Finally, I put a letter 'G' drill (tapping size for 5/16" BSF) right through both lugs.  A jobber length drill was just about long enough.  If the saddle is wound too close to the head-stock, the casting nudges the counter-shaft clutch lever into neutral!

After a bit of a search, the shed gremlins did yield up a set of 5/16" BSF taps - LEFT-HAND!!          

[awemawson]

I've got normal RH 5/16 bsf if you want to borrow them Pete

[Pete W.]

I've got normal RH 5/16 bsf if you want to borrow them Pete

Hi there, Andrew,
Thank you for your kind offer          but I'm waiting          for the Postman to bring me a couple of long series taps. 
My toy budget is well O/D this month, it's a good thing we don't pay Council Tax in February or March!          

   The new MSC catalogue arrived this afternoon, wow, that's heavy! 
Thing is, I've been getting FOUR copies of 'Advantage' each month, if MSC are using the 'Advantage' mailing list for the catalogue .....          

[awemawson]

Yes mine arrived as well. Did you notice the 20% off coupon on the box ?

[Pete W.]

Hi there, all,

Yes mine arrived as well. Did you notice the 20% off coupon on the box ?

No, Andrew, actually I didn't.  It wouldn't matter if I had, my piggy-bank for toys has been sealed for the foreseeable future!          

Well the Postman delivered a few 5/16" BSF taps yesterday but I didn't get to use them until this afternoon.

Here's a photo (staged after the event) showing the letter 'G' drill completing the tapping size hole:



Next, starting the taper tap in the left-hand lug:



That one called for careful coordination between pulling on the head-stock drive belt to turn the tap and advancing the tail-stock to push the saddle & casting towards the tap.  I followed with the second and plug taps free-hand.  Then I threaded a taper nut-tap through the left-hand lug, clamped its shank in the drill chuck and presented it to the right-hand lug, like so:



Once that tap had started in the hole, I removed the casting from the lathe and finished tapping that hole by hand on the bench and followed it up with a plug nut-tap.  Here's a photo of that stage (sorry about the fuzzy picture):



Then I did a trial assembly of the gear cover, back-plate, hinge-screws and lock-nuts:



It's not perfect but I think, with a bit more adjustment in situ, it'll do.

I realise that some readers will think this has all been simple stuff and why am I describing it.  Well, the big theme of this stage of the project has been holding an awkward shaped casting and I've achieved that using simple improvised materials - maybe that will encourage someone and help with their project.

The next operation on the gear cover is to drill and tap the 2 BA hole for the spring clip that holds it in the closed position.  I still don't have the clip to hand so I'm having to set the gear cover aside for a while. 

So I'm turning my attention to actually attaching the gearbox to the lathe.  The first step in that process is to drill and tap the two holes in the lathe bed to take the 1/4" BSF gearbox fixing screws, my ML7 is too early to have had those holes drilled and tapped in the Beeston Myford factory.  The third gearbox mounting screw fits into the lower of the two tapped holes used by the left-hand lead-screw bearing.  Here's a photo:



I was able (long, long ago) to buy a drilling jig from Beeston Myford, it's the top one in this photo:



The 'official' procedure, according to Beeston Myford's Instructions for fitting the gearbox, is to first remove the two head-stock push-screws (they're the ones whose slotted ends you can see in the photo) and attach the drill jig using two 1/4" BSF cap-head screws through the outermost holes in the jig.  Then you drill two 1/4" BSF tapping-size holes into the lathe bed, using the jig's other two holes as a guide.  Then, you remove the jig and open out the two inner holes to 1/4" diameter, remount the jig and tap the bed holes 1/4" BSF using the opened-out holes to guide the tap.  The jig can then be removed and the head-stock push-screws replaced. 
However, the jig can't be re-used.

For some reason I now can't recall, I wasn't happy with that procedure, so I reproduced the jig's holes in a new piece of material.  I then turned the new piece end-over and spotted through another pair of holes - fortunately, they all happen to be spaced in a way that avoids hole positions clashing.  I then opened up the last pair of holes to 1/4" BSF clearance size - N.B. that's bigger than 1/4", the tap cuts with clearance at the thread crests. 
I stamped up the holes, 'F' for fixing, 'D' for drilling and 'T' for tapping.  The amended design jig is the lower one in the photo.  They look like brass in the photo - that's a trick of the light, they're actually both mild steel. 
The stampings don't show in the photo, partly because I cleverly arranged the over-printing to hide some of them!          
So, I've got a drilling-jig that can be re-used.  Roll-up, roll-up, get your ML7 lathe beds drilled and tapped 'ere', the line forms on the left!  Er, NO!          

That lathe sure looks grubby in the photo.  Someone else's post here on Mad Modders mentioned using sugar soap to get rid of the oily stains - maybe I'll try it. 

[Pete W.]

Hi there, all,

I managed to grab an hour or so in the workshop this afternoon and drilled and tapped the holes in the ML7 bed that support the top of the QC gearbox.  I summarised the procedure in my previous post so I won't repeat it all, just a few words with each photo.

Here is the jig, mounted to the lathe bed in the drilling position.  I've included the drill-bit in the photo but omitted the drill because I couldn't support the drill and handle the camera at the same time (no room for my lovely but shy assistant, in any case, she was busy elsewhere!).  I'm sorry about the poor focus - the camera was having a bad day!  The bit of masking tape round the shank of the drill bit tells me when the depth of the hole gets to Beeston Myford's specified maximum depth, i.e. 0.625".  It's a solid carbide, stub-length drill, bought specifically for this job.



The next photo shows the jig turned end-over-end to the tapping position and the tapping in progress.  I hi-jacked my lovely but shy assistant's aerosol of 'canned air', complete with snorkel tube', to blow out the swarf.  (She's an MS-Windows nerd and I'm an occasional computer widower!          )  As the lathe bed is cast iron, I drilled and tapped dry (but with care).  The taps are a brand new HSS set, again bought specifically for this job. 
I wonder whether this operation would be feasible on an ML7 with an induction hardened bed?          



Finally, here is the view with the jig removed, a couple of cap-head screws in the new tapped holes and the head-stock push screws returned to their holes.  I took care to label them on removal and to replace each in the hole it came from.  By comparing the orientation of the screw slots in this photo with those in the photo in the previous post, you can judge how well they went back into their original position. 



Well, that's probably all simple and basic stuff but I make no apologies - it's just a joy to me to be making progress.

The next instalment is to clean and critically examine the lead-screw and compare it with one of gear-box length I have in stock.  I'll use the one with the least worn thread but if that is the original, I'll have to shorten it.  After that, I'll start stripping off the change gear quadrant and back-plate including the tumbler reverse. 

[awemawson]

Coming along nicely Pete - you'll have that QC box on in no time. You've made quite an investment in tools for that job alone.

I spent the day running about keeping plates spinning on poles Power cut just before midnight, sewage system needs power to not over flow, cottages full of guests who you can't tell to cross their legs ! Front gate mains powered, no one can get out or in. UKpowernetworks needed access to their switch gear. Too many things all at once, I need a gin and tonic!  Jury rigged 3 kw genny to power the sewage system so that was thumping away all day. Unscrewed gate actuator so it can be manually opened and wedged it open with 20 kg sack of goose food ! Managed to get one coat of paint on that 4th axis thingy under torch light ! Power back on 6 pm - run around undoing that that had been done, reset half a dozen timeswitches, reboot  several brace of pc's and routers - relief - need another g&t.

[Pete W.]

Hi there, Andrew,

Thank you for your post.  Wow, I think I rather have the day I've had than the one you've had!!! 
G&T, hmmm, somewhere in the sideboard here I've got a bottle of some blue stuff that I never get the right circumstances to enjoy.          

Back in 1988 I had a spell in the bandage factory and got quite pally with the medical student who used to come and chat to me when his superiors weren't looking.  He spoke of something called 'the J-curve'.  It's a plot of harm versus alcohol intake and it's called 'the J-curve' because from zero alcohol up to X units, the harm is negative, after that graph crosses the axis and harm rises steeply with increasing intake. 
The snag is, nobody would tell me the value of X!!          

We had a power glitch this afternoon, just a few seconds as though the supply was switching over from one source to another.  I was in the workshop at the time while it was hailing outside - makes quite a noise on the new roof.  My lovely but shy assistant was 'at the computer' but didn't notice any glitch, I haven't yet looked at the bedside alarm clock radio, I expect it all wants resetting.          

A friend of ours a couple of miles from here lost power at 18:00 last night and it was still off at 10:30 this morning.  Like you, they have an electric gate and were to go to a wedding up around the M25.  He did manage to get their car out but he has some kit that relies on UPS back-up and all the UPS batteries had run right down.  They are currently on our kitchen floor, hopefully recharging.  Trouble is, the chargers he brought in with the batteries only manage 600 mA so I doubt whether they'll put much of a charge in in the time available.  They're gel-electrolyte batteries and need a constant voltage charger.  I'm going to suggest to him that he gets whatever sort of a charger folks use with those 'pavement buggies', apparently they'll recharge the buggy battery overnight. 

[tom osselton]

The snag is, nobody would tell me the value of X!!   

That's because we can always drink too excess but don't always know Y!!   

[awemawson]

Slippery slope booze ! Just a little lowers your sense threshold.

(Ordered up a generator change over switch and bits today so things can be a bit less scary next time - but when I install it it'll ensure the need never recurs !)

[Pete W.]

Hi there, all,

The latest stage in this project is 'Lead-Screw Modification - Part 1'.

I started with a bit of a set back, the spare lead-screw that I thought was the right length for the gear-box turned out to be standard length.  So, whichever lead-screw I use, I'd have to shorten it.          

I'd like to finish the shortened end in the lathe but the bore through my head-stock is 19/32" and the lead-screw diameter is 5/8".  Hmmm.       
And, of course, the lead-screw is too long to work on with one end on the chuck and the outer end in the fixed steady, the lathe carriage would be in mid-air!          
The 'spare' lead-screw is of the two-piece type, connected by a collar and a couple of roll-pins. 
If I use that one, maybe I can detach the short head-stock end section and mount that in chuck & fixed steady and finish the cut end in the lathe.      
Here are the two lead-screws, the original one above and the 'spare' one below:



So, lets's start and see how we get on.  First, remove the left-hand (head-stock end) lead-screw bearing bracket.  This revealed something that forced the which lead-screw decision - the original lead-screw doesn't have the woodruff key slot required by the gearbox output gear (see below).

Here are the head-stock ends of both the lead-screws, the original one above and the 'spare' one below:



OK, now we know which lead-screw we're going to use.  But to get the measure of the amount to be removed, I need to fit the 'spare' screw in place of the original one.  So, up to the tail-stock end to remove the lead-screw hand-wheel, cross-pin (a parallel dowel) and thrust collar.



That area of the lathe has been undisturbed since about 1971 and those parts have got used to being together.  Still, with a little bit of gentle persuasion, I got them all apart and swapped lead-screws.  However, I couldn't refit the cross-pin, it just didn't want to go into the cross-hole in the lead-screw end.  (The hole for the cross-pin is in the shadow to the right of the lead-screw bearing bracket.)  Eventually, I proceeded without fitting it, I'll give it serious attention when I get to the final assembly stage.  So, back to the head-stock end.

The Beeston Myford instructions say 'feed the gearbox onto the leadscrew and secure it in position with the three screws', that's two 1/4" BSF by 3/4" cap-heads in the two holes I drilled & tapped last time and a lower screw that goes into one of the holes previously occupied by the lead-screw bearing bracket fixings.  Well, the top two are a bit fiddly but manageable.  The lower one, described in the instructions as 'captive', escaped into the bowels of the gearbox!           It's got a slotted mushroom head so you can't hold it on the end of an Allen key and the gear-box innards conceal it from view!          
So, again, I pressed on without doing that one up.  I fitted the woodruff key, then the gear-wheel, spaced off the end of the gear-box casing by with a 15 thou feeler gauge (the shed gremlins had surrendered the feeler gauge set without too much of a fight           ).  That got me to this stage:



The Beeston Myford instructions say that I've got to shorten back that left-hand shaft so that not more than 31 thou is left protruding from the face of the gear hub. 
So I've measured the total protrusion.  Now I've got to take it all apart again and shorten the lead-screw, i.e. actually cut metal, where's the chewing finger-nails smiley?

So, once I've done that, I anticipate three issues:

1. If I drive out one of the roll-pins and just work on the short section of lead-screw, will it all go back together without prejudicing my measurement?

2. How do I get the cross-pin back into the tail-stock end of the lead-screw without damaging anything?

3. Shall I go crazy trying to get that lower gear-box fixing screw into position?

Here endeth 'Lead-Screw Modification, Part 1'.            

[Pete W.]

Hi there, all,

Here is 'Lead-Screw Modification - Part 2':

I drove out one of the roll-pins securing the stub extension shaft to the main part of the lead-screw.  However, the stub was a very tight (like un-movable!) fit into the collar.  I could probably have got it out but it was obvious that it would be as difficult, if not more so, to replace it in the collar so that the roll-pin holes would line up.  So I refitted the roll-pin, quick!

It had been my intention to make a guide sleeve to fit over the stub shaft to be secured in position with a couple of grub screws and positioned so that its end face defined the end of the shaft after shortening.  I proceeded to make that sleeve, now to be used to aid the shortening of the complete lead-screw plus stub shaft by hand.  My workshop stock is still in disarray after the roof leak & flood so the only suitable diameter steel I could find was some Peter Stubs silver steel.

According to my measurement yesterday, the length of shaft protruding from the drive gear was 2.094 inches.  Beeston Myford's instructions specify that, after shortening, the protrusion should be not more than 0.031 inches.  I chose to aim for a protrusion of 16 thou so I positioned the sleeve a distance of 2.078 inches from the end of the stub shaft like so:



(That picture was taken after I had started to hacksaw off the excess shaft.)  The 'back-up' ring is actually the one that previously secured the final driven change-wheel on the end of the original lead-screw.  I didn't want it to be the 'front-line' guide for the hacksaw but it seemed prudent to fit it to minimise the possiblilty of the main guide sleeve moving - I didn't tighten the grub-screws too tight for fear of making dents in the stub shaft.  In the event, the hacksaw did cut into the face of the guide sleeve so I backed the sleeve off a few thou before cleaning up the cut end of the shaft with a file.  I chamfered the shaft end with the file, it's not as neat as it would have been if I'd been able to do it all in the lathe.

I'd noticed that the slotted ends of the head-stock push-screws were a few thou proud of the edge of the lathe bed to I removed each in turn and filed enough from its inner end to make the screws under-flush.  Then I refitted the lead-screw to the lathe, fed the gear-box onto it and inserted the gear-box fixing screws into their tapped holes in the bed.  It's necessary during this operation to ensure that the O-ring is in position aound the lower screw-hole.  Viewing the interior of the box with the aid of a torch revealed that my fears about the lower fixing screw had been unfounded, it was still in-position and I was easily able to screw it up.  What the torch did reveal, though, was a quantity of steel swarf lying on the bottom of the gear-box.  How on earth did that get there??           Removing that will need long tweezers.

All of that brought me to this stage:



Here's a closer view:



The file marks on the end of the shaft are really prominent in that photo, they're not as bad as they look!          
I measured the protrusion of the shortened shaft from the gear hub at about 6 thou.  That's less than I aimed for but it's less than the critical 31 thou so it'll do.  It does depend a bit on the set-up of the clearances at the tail-stock end of the lead-screw.

The next stage of this project is to fit the cross-pin at the tail-stock end of the lead-screw and then re-assemble the lead-screw hand-wheel and simmonds nut.  Then I have to check that the top surface of the gear-box casing (with the lid removed) is parallel to the plane of the lathe bed surface and that the gear-box and lead-screw rotate freely.  After that, I have to fit the gear back-plate, then to refit the gear quadrant and tumbler gears and confirm freedom of the whole chain to rotate.  Somewhere about there, I have to fill the gear-box to the correct level with SAE 30 motor oil. 

Then I shall return to the gear cover - I've one more hole to drill and tap and then I have to paint it! 

[lordedmond]

Pete

Now you have it sorted do you know that to cut metric threads all you need is a 33t and a 34 t gear to replace the output gear from the banjo if my brain cell is working its a 24 t

these are not to nasa standards but are very very close and cheaper that the metric kit ale you retain most of the fine feeds

Stuart